Abstract:

The ability to adaptively shift between exploration and exploitation control
states is critical for optimizing behavioral performance. Converging evidence
from primate electrophysiology and computational neural modeling has suggested
that this ability may be mediated by the broad noradrenergic projections
emanating from the locus coeruleus (LC-NE; Aston-Jones & Cohen, 2005).
There is also evidence that pupil diameter covaries systematically with LC
activity. Though imperfect and indirect, this link makes pupillometry a useful
tool for studying the LC-NE system in humans and in high-level tasks. Here we
present a novel paradigm that examines how the pupillary response during
exploration and exploitation covaries with individual differences in fluid
intelligence during analogical reasoning on Raven's Advanced Progressive
Matrices (APM). Pupillometry was used as a non-invasive proxy for LC activity,
and concurrent think-aloud verbal protocols were used to identify exploratory
and exploitative solution periods. This novel combination of pupillometry and
verbal protocols from 40 participants revealed a decrease in pupil diameter
during exploitation and an increase during exploration. The temporal dynamics
of the pupillary response was characterized by a steep increase during the
transition from exploitative to exploratory periods, sustained dilation for many
seconds afterwards, followed by gradual return to baseline. Moreover, the
individual differences in the relative magnitude of pupillary dilation accounted
for 16\% of the variance in APM scores. Assuming that pupil diameter is a valid
index of LC activity, these results establish promising preliminary connections
between the literature on LC-NE mediated cognitive control and the literature on
analogical reasoning and fluid intelligence.